1. Field of the Invention
The present invention relates to rectifier diode technology and more particularly, to such a rectifier diode, which has one or multiple bare chip diodes be directly placed on a substrate and uses a metal interface layer and a conductive metal thin film and predetermined electrode pins and bond pads to secure the bare chip diodes and the substrate tightly together and to electrically couple the bare chip diodes to the circuit in the substrate, eliminating a further packaging process, simplifying the manufacturing process and reducing the manufacturing cost.
2. Description of the Related Art
With fast development of electronic technology, rectifier diodes are used intensively in different electronic devices to rectify electric current. Taiwan Patent No. 101281, Publication No. 3421841, filed on Sep. 30, 1997, discloses a semiconductor diode device and its fabrication method. According to this design, as shown in FIG. 12, one respective ends of the positive and negative poles of an bare chip diode A2 are bonded to a circuit unit A1 of a substrate A, an adhesive A3 is covered on the substrate A over the bare chip diode A2 and precisely ground to let the other ends of the positive and negative poles of the bare chip diode A2 be exposed to the outside, and then a conducting circuit A4 is formed on the exposed ends of the positive and negative poles of the bare chip diode A2 by printing or vacuum deposition to electrically coupled to the bare chip diode A2 to the circuit in the substrate A, and then a protective cover layer A5 is molded on the substrate A. This method needs to perform adhesive bonding, grinding and wire bonding and encapsulating procedures, complicating the fabrication. Further, the performance of the grinding step tends to result in a precision error, leading to a defective product. Further, the wiring bonding and encapsulating procedures need to use different processing tools, increasing the equipment installation cost and the product fabrication cost.
Further, flip chip rectifier diodes are most popularly used in electronic products at the present time. After fabrication of bare chip diodes, they must be packaged by IC packaging companies. As shown in FIG. 13, bumps B1 are provided at the bottom side of the bare chip diode B, and then tin solder B2 is bonded between the bumps B1 and a carrier plate B3 to electrically couple the bare chip diode B to the circuit at the carrier plate B3. Further, an encapsulation or underfill process is then performed to finish the fabrication. This method has the drawback of high cost. Further, during operation of the bare chip diode, waste heat can be transferred through the bumps B1 and the tin solder B2 to the carrier plate B3 for dissipation. However, due to limited heat transfer area, waste heat cannot be quickly transferred to the carrier plate B3 for dissipation. Further, the presence of the bumps B1 and the tin solder B2 greatly increase the height of the finished product, not suitable for low profile application.
In the aforesaid flip chip rectifier diode structure and its fabrication method, bumps B1 or tin coating must be made prior to the process of bonding the bumps B1 or the bare chip diode B to the carrier plate B3. If gold is used to make the bumps B1, the cost will be very high. If silver or tin is used to reduce the cost, the product reliability will be relatively lowered. In order to improve heat transfer problem, an underfill process is necessary to fill a conducting adhesive between the bare chip diode B and the carrier plate B3. However, this added underfill process complicates the manufacturing process, extends the manufacturing time, and increases the manufacturing cost.
Therefore, it is desirable to provide a rectifier diode that eliminates the problems of the aforesaid prior art designs.